Ultraviolet A and photosensitivity during vemurafenib therapy.


Panel A shows the minimal erythema dose of ultraviolet B (UVB) (upper row of fields) and ultraviolet A (UVA) (lower row of fields). The fields irradiated with UVA showed increasing erythema 24 hours after irradiation. The UVB-irradiated fields did not show any erythema or pigmentation. Panel B shows UVA-induced reddening and swelling 24 hours after irradiation. Panel C shows the UVA minimal erythema dose. Prior to irradiation, the irradiation field for UVA was divided into two parts with a covering film. Erythema was prevented by a sunscreen product specifically tailored for UVA. To the Editor: Vemurafenib (PLX4032, Zelboraf) is a selective inhibitor of V600E BRAF.1 In phase 1, 2, and 3 clinical trials involving patients with tumors that have V600E BRAF mutations, vemurafenib was associated with consistent efficacy and improved survival.2,3 These data led to approval of vemurafenib for use in the United States and Switzerland. Common toxic effects observed with vemurafenib include arthralgia, rash, fatigue, and photosensitivity.4 In our experience, some patients have had a severe sunburn reaction consisting of painful blistering. This reaction has affected their daily activities, including driving; such patients experience photosensitivity through glass while driving a car. To advise patients about the most appropriate photoprotection measures, it is essential to identify the responsible ultraviolet spectrum. Therefore, we determined the minimal erythema dose (i.e., the lowest dose that results in visible erythema on depigmented skin) using ultraviolet irradiation devices (Waldmann Lichttechnik). For ultraviolet B (UVB), the emission spectrum included wavelengths from 285 to 350 nm (peak, 310 to 315), and for ultraviolet A (UVA), the emis-


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